/**
 * SM4Algorithm实现（国密Algorithm）
 * 参考：GB/T 32907-2016
 */

#include "sm4_impl.h"
#include <string.h>

/* SM4 S盒 */
static const uint8_t SM4_SBOX[256] = {
    0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
    0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
    0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
    0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
    0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
    0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
    0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
    0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
    0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
    0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
    0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
    0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
    0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
    0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
    0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
    0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
};

/* 系统ParametersFK */
static const uint32_t SM4_FK[4] = {
    0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
};

/* 固定ParametersCK（32个） */
static const uint32_t SM4_CK[32] = {
    0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
    0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
    0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
    0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
    0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
    0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
    0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
    0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
};

/* Basic运算：获取字节 */
#define GET_BYTE(x, n) (((x) >> (24 - (n) * 8)) & 0xff)

/* Basic运算：合成字 */
#define MAKE_UINT32(b0, b1, b2, b3) \
    (((uint32_t)(b0) << 24) | ((uint32_t)(b1) << 16) | ((uint32_t)(b2) << 8) | (uint32_t)(b3))

/* Loop左移 */
#define ROTL(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

/* S盒变换（字节替换） */
static uint32_t SM4_Sbox(uint32_t x)
{
    return MAKE_UINT32(
        SM4_SBOX[GET_BYTE(x, 0)],
        SM4_SBOX[GET_BYTE(x, 1)],
        SM4_SBOX[GET_BYTE(x, 2)],
        SM4_SBOX[GET_BYTE(x, 3)]
    );
}

/* 线性变换L（用于加解密） */
static uint32_t SM4_L(uint32_t x)
{
    return x ^ ROTL(x, 2) ^ ROTL(x, 10) ^ ROTL(x, 18) ^ ROTL(x, 24);
}

/* 线性变换L'（用于Key扩展） */
static uint32_t SM4_L_Prime(uint32_t x)
{
    return x ^ ROTL(x, 13) ^ ROTL(x, 23);
}

/* T变换（用于加解密） */
static uint32_t SM4_T(uint32_t x)
{
    return SM4_L(SM4_Sbox(x));
}

/* T'变换（用于Key扩展） */
static uint32_t SM4_T_Prime(uint32_t x)
{
    return SM4_L_Prime(SM4_Sbox(x));
}

/* Key扩展Algorithm */
void SM4_Impl_Init(SM4_Impl_Context* ctx, const uint8_t* key)
{
    uint32_t K[36];  // K[0..3]ForMK，K[4..35]Forrk
    uint32_t i;
    
    /* LoadMK（主Key） */
    for (i = 0; i < 4; i++) {
        K[i] = MAKE_UINT32(key[i*4], key[i*4+1], key[i*4+2], key[i*4+3]);
        K[i] ^= SM4_FK[i];
    }
    
    /* Generate32个轮Key */
    for (i = 0; i < SM4_IMPL_ROUNDS; i++) {
        K[i + 4] = K[i] ^ SM4_T_Prime(K[i+1] ^ K[i+2] ^ K[i+3] ^ SM4_CK[i]);
        ctx->round_key[i] = K[i + 4];
    }
}

/* SM4加密（单块） */
void SM4_Impl_Encrypt_Block(const SM4_Impl_Context* ctx, const uint8_t* input, uint8_t* output)
{
    uint32_t X[36];
    uint32_t i;
    
    /* LoadPlaintext */
    for (i = 0; i < 4; i++) {
        X[i] = MAKE_UINT32(input[i*4], input[i*4+1], input[i*4+2], input[i*4+3]);
    }
    
    /* 32轮迭代 */
    for (i = 0; i < SM4_IMPL_ROUNDS; i++) {
        X[i + 4] = X[i] ^ SM4_T(X[i+1] ^ X[i+2] ^ X[i+3] ^ ctx->round_key[i]);
    }
    
    /* 反序变换OutputCiphertext */
    for (i = 0; i < 4; i++) {
        uint32_t val = X[35 - i];
        output[i*4]     = (val >> 24) & 0xff;
        output[i*4 + 1] = (val >> 16) & 0xff;
        output[i*4 + 2] = (val >> 8) & 0xff;
        output[i*4 + 3] = val & 0xff;
    }
}

/* SM4解密（单块） - Use反序的轮Key */
void SM4_Impl_Decrypt_Block(const SM4_Impl_Context* ctx, const uint8_t* input, uint8_t* output)
{
    uint32_t X[36];
    uint32_t i;
    
    /* LoadCiphertext */
    for (i = 0; i < 4; i++) {
        X[i] = MAKE_UINT32(input[i*4], input[i*4+1], input[i*4+2], input[i*4+3]);
    }
    
    /* 32轮迭代（Use反序轮Key） */
    for (i = 0; i < SM4_IMPL_ROUNDS; i++) {
        X[i + 4] = X[i] ^ SM4_T(X[i+1] ^ X[i+2] ^ X[i+3] ^ ctx->round_key[31 - i]);
    }
    
    /* 反序变换OutputPlaintext */
    for (i = 0; i < 4; i++) {
        uint32_t val = X[35 - i];
        output[i*4]     = (val >> 24) & 0xff;
        output[i*4 + 1] = (val >> 16) & 0xff;
        output[i*4 + 2] = (val >> 8) & 0xff;
        output[i*4 + 3] = val & 0xff;
    }
}
